The world wide web (“the web”) permits companies and individuals to electronically publish content in the form of web pages that can be retrieved and displayed using a browser program running on a client computer system. Such “publishers” often sell to advertisers opportunities to present advertising messages together with their published content.
For example, an advertiser who is a music publisher may purchase opportunities to present an advertising message promoting a new music CD published by the publisher. The advertising message may be “rich” in a variety of ways. They may, for example, include text identifying the title of the CD and the responsible artist in a style that is visually compatible with an appealing background pattern and/or color, a series of multiple photos of the artist, a link to a web page on which the user can listen to the artist's music and purchase the CD, etc. Some publishers, in addition or instead of such rich advertising messages, provide advertisers opportunities to present textual advertising messages, which generally include only text and a link to a web page associated with the advertising message. Some textual advertising messages are search advertising messages, which specify one or more keywords, and are presented in search result web pages served by a publisher in response to a user query containing at least one of the specified keywords. Because textual advertising messages do not contain any rich content, they can be relatively straightforward to create, rendering them accessible to a wide range of advertisers.